Additionally, this application is related to the application xe2x80x9cINJECTION MOLD FOR AN OPTICAL SEMICONDUCTOR PACKAGE AND CORRESPONDING OPTICAL SEMICONDUCTOR PACKAGE,xe2x80x9d Ser. No. 09/862,984, now pending, which was filed on the same day as the present application and commonly assigned herewith to STMicroelectronics S. A. This related application is herein incorporated by reference.
1. Field of the Invention
The present invention relates to semiconductor packages, and more specifically to a mold for the injection molding of an encapsulation material to encapsulate an integrated circuit chip.
2. Description of Related Art
Currently, an injection mold includes two parts which between them define an injection circuit that includes at least one injection cavity intended to house an integrated circuit chip, at least one transfer chamber from which the encapsulation material is injected, and at least one injection channel connecting the transfer chamber to the injection cavity.
During the encapsulation process, due to the effect of the high injection pressure created in the transfer chamber, liquid encapsulation material may seep between the two parts of the mold and out of the injection circuit. Such seepage is greater when the injected encapsulation material is very liquid (for example, when it consists of a molding resin based on an unfilled or lightly filled epoxy). During demolding, the resulting molded part then has xe2x80x9cflashxe2x80x9d, which consists of films of encapsulation material attached to the material that has filled the injection circuit. This flash is particularly irksome when subsequently handling the molded part, because the flash detaches and disintegrates.
The same problem arises when the mold includes at least one insert with a transverse face that partly constitutes the wall of the injection cavity. Here too, encapsulation material can seep between the insert and the mold, so as to also produce flash attached to the material that has filled this cavity. Such flash is particularly irksome when the chip includes a surface provided with an optical sensor and when the flash forms near this face.
In view of these drawbacks, it is an object of the present invention to overcome the above-mentioned drawbacks and to provide a mold for injection molding an encapsulation material to encapsulate at least one integrated circuit chip. Preferably, the mold includes at least two parts defining at least one injection circuit that includes at least one injection cavity for housing the chip, at least one transfer chamber from which the encapsulation material is injected, and at least one injection channel connecting the transfer chamber to the injection cavity.
One embodiment of the present invention provides an injection mold for injection molding an encapsulation material to encapsulate at least one integrated circuit chip. The injection mold includes at least two parts that define at least one injection circuit, and at least one blind complementary channel communicating with the injection circuit. The injection circuit includes at least one injection cavity for housing the chip, at least one transfer chamber from which the encapsulation material is injected, and at least one injection channel connecting the transfer chamber to the injection cavity. The blind complementary channel is formed between the two parts of the mold and forms at least one appendage of encapsulation material that is connected to the encapsulation material that fills the injection circuit. In a preferred embodiment, the complementary channel extends from the injection channel.
Another embodiment of the present invention provides a method for injection molding an encapsulation material to encapsulate at least one integrated circuit chip. According to the method, a leadframe supporting the chip is placed in an injection mold having at least one injection circuit. The injection circuit of the mold includes at least one injection cavity for housing the chip, at least one transfer chamber from which liquid encapsulation material is injected, and at least one injection channel connecting the transfer chamber to the injection cavity. The liquid encapsulation material is injected into the injection cavity via the injection channel so that the liquid encapsulation material fills the cavity and at least one blind complementary channel of the injection mold that communicating with the injection circuit. The liquid encapsulation material is hardened so as to form a molded part that includes an integrated circuit package corresponding to the injection cavity and at least one complementary branch of encapsulation material corresponding to the at least one blind complementary channel, with the complementary branch of encapsulation material being connected to the hardened encapsulation material filling the injection circuit. In one preferred method, the complementary channel connects two injection channels of the mold that are connected to the transfer chamber.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only and various modifications may naturally be performed without deviating from the present invention.